Spark gap electrical apparatus



1 M. E. HAlNE ET AL SPARK GAP ELECTRICAL APPARATUS Filed March 25, 1945 S m m E V m ATTQR N: YS

Patented Dec. 30, 1947 SPARK iGAPzELECTRICAL APPARATUS,

Michael Edward Haine, John Millar Meek, and

JohnDrummond 'Craggs, Sale, England, as-

1 signors to Metropolitan-Vickers Electrical Company Limited, London, England, a companyof Great Britain,

. Application March 23, 1945, Serial No. 584,304. In GreatBritain June 21, 19.43

:Section'; L Public Law 690,'August 8,. 1946 v.vlatent:expires June 21, 1963 3:.Claims.

This invention relates apparatus',-and-= comprises an improvement in or modificationot the arrangements disclosed in PatentNo; 2;400,456;:granted-'May 14, 1946, and

in application Ser. No, 514,865, filed December Thesaid patent andapplication relate to a.trippable spark gap device of'the kind comprising input and output main electrod'es'fixed" 'ap-artappreciably. beyond their normal sparkover spac-- ing. in. relation to a predetermined voltage tosbe normally. applied across the. gap,. a fixed trigger -.electrode.associated with one. of said main-electrodes, an-envelope enclosing. said electrodessand .at least one inert gas mixed with a small pro- The' main ob ect of the present invention is to improve the reliability of operation of such a device and ensure that breakdown shall always occur when a trigger voltage of predetermined value is applied.

According to the present invention, an insulating tube of appreciable specific inductive capacity and with a relatively thick wall encircles said trigger electrode over an appreciable portion of its length and is internally spaced from said trigger electrode by a relatively small amount to form an annular gap, and an electrical conductor is located externally of the insulating tube and is electrically connected to said apertured electrode, the arrangement being such that when a triggerin pulse is applied between the electrical conductor and the trigger electrode an intense electric stress is set up in said annular gap producing corona discharge.

In the drawin Fig. 1 is a detail sectional view of the electrodes of the improved spark gap electrical apparatus.

Fig. 2 is a view partly in elevation and partly in section, of the envelope and the electrodes mounted therein and which envelope encloses the gas surrounding the electrodes.

Referring to Fig. 1 of the accompanying drawing, which shows a modification of the form shown in the aforesaid application and patent,

to spark zgapelectrical at IllI is shown the. anode whichcomprises the spherical end portion only: it is=supported by the posts I02 which are butt-welded to the tungstenleads I03 sealed through the glass foot. I04 of the mainbulb. The trigger wire is shown at I05. At I06. is shown theinsulating tube which in this case is. shown asa glass "bead which. at its left-hand end is fixed by fusion to the glass foot I04. This glass bead has anaxial hole providing, as shown, a distinct clearance withre- .spect to the trigger wire I05 passing through. it.

Itis in this appreciable annular gap that, due tothe higher electrical stress, the corona is set up requisite for irradiating. the main spark..gap. This is due tothe high electricalstress setup in the annular gap as a result of the insulating tube which, due to its high specific inductive capacity, concentrates the voltage gradient in the gap. To enhance this efiect the bead, in the figure, is of considerable thickness compared with that shown in Fig. 5 of the drawings accompanying the aforesaid specification, and is closely surrounded by the nickel or other metal sleeve I0'I which does not extend to the right-hand end of the glass insulating bead I06. The sleeve IN is connected to the anode support I02 by a wire or strip I08. In the alternative equivalent arrangement (not shown) the glass insulator I06 is replaced by a material having an appreciably higher dielectric constant than glass, such as Rutile, or a rutile material known in the trade as Faradex. In such case the metal sleeve I01 can be omitted as the triggering voltage will be applied between the anode support I02 and the trigger electrode I05. It is however preferable to employ the metal sleeve I01.

In Fig. 2, which shows how the structure is mounted in an envelope, I09 indicates the oathode, IIIl the envelope in which the complete structure is mounted, and I I I is the base to which the envelope is secured. H2 and H3 are respectively the terminals to which are secured leads from the trigger electrode I05 and the supporting pillar I02 for the anode IOI.

According to the present invention, a high electrical stress is produced in the gap between the trigger electrode I05 and the glass bead I06. This is due to the fact that the glass head has an appreciably higher dielectric constant than that of the air ap, and consequently the voltage drop between the anode and the trigger electrode I05 will be concentrated in the air gap around the trigger electrode I05, causing high electrical stressin in this gap. The purpose of the metal sleeve I01 connected to the anode IOI by the con- 3 ductor I08 is to provide an electrode at anode potential which is closed against the exterior surface of the glass bead Hi6 and thus obtain the maximum amount of electrical stressing. In

cases in which the glass bead I06 is replaced by duces ionization in the gap around the trigger electrode I05, and that the ions so produced will emerge from the ga and will pass between the sparking tips of the electrodes and this efiect' will reduce the electrical stress necessary to pro duce a spark.

aperture and spaced a predetermined distance from the sides of the aperture such as to ensure a breakdown when a trig ering pulse is applied to the trigger electrode, in combination with an insulating tube of appreciable specific inductive 7 capacity and relatively thick wall encircling said What we claim as new and desire to secure by Letters Patent of the United States is:

1. A trippable spark gap device of the kind comprising input and output main electrodes fixed apart appreciably beyond their normal sparkover spacing in relation to a predetermined voltage to be normally applied across the gap, fixed trigger electrode adjacent one of said main electrodes, an envelope enclosing said electrodes, and at least one inert gas mixed With a small proportion of a quenching gas filling said envelope at a pressure above atmosphere, said trigger electrode being formed with a relatively small radius of curvature at the arcing tip and the main electrode adjacent the trigger electrode trode protruding into the neighborhood of the trigger electrode over an appreciable portion of its length and internally spaced from said trigger electrode by a relatively small amount to form an annular gap, and an electrical conductor located externally of the insulating tube and electrically connected to said apertured electrode.

2. A trippable spark gap device as defined in claim 1, wherein said electrical conductor comprises an'electrical lead to said apertured electrode which'is spaced from the exterior of said insulating tube.

3. A trippable spark gap device as defined in claim 1, wherein said external conductor is formed by a metal sleeve closely surroundin said insulating tube.

MICHAEL EDWARD HAINE. JOHN MILLAR MEEK. JOHN DRUMMOND CRAGGS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,304,868 Franklin May 27, 1919 1,727,956 Billotte et al Sept. 10, 1929 1,803,976 Quarrie May 5, 1931 1,944,929 De Forest Jan. 30, 1934 

